1910 Census Code

1910 Census Code

In the 1910 U.S. Census Column 30 asks "whether a survivor of Union or Confederate Army or Navy?" What does the code "8" mean? Also in Column 31 it asks "whether blind (both eyes)?" What does the code "6" mean?

You can't believe how many people I have asked and NO ONE can tell me. So thanks for any help that anyone can give me!!!!